Question: Simplify the following expression: $q = \dfrac{k}{8} - \dfrac{4k}{7}$
Answer: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $8$ and $7$ $\lcm(8, 7) = 56$ $ q = \dfrac{7}{7} \cdot \dfrac{k}{8} - \dfrac{8}{8} \cdot \dfrac{4k}{7} $ $q = \dfrac{7k}{56} - \dfrac{32k}{56}$ $q = \dfrac{7k -32k}{56}$ $q = \dfrac{-25k}{56}$